The present invention generally relates to a method and apparatus that can be utilized to significantly reduce the biological load on consumer products such as food products, botanicals, cosmetic ingredients and medical products, which have traditionally been treated with commercial sterilants or furmigants such as ethylene oxide, propylene oxide, methyl bromide, hydrogen phosphide, steam (heat), irradiation, and the like.
Currently, ethylene oxide (EO) is the agent of choice for virtually all of the gaseous sterilization of consumer products performed in the United States. EO, however, has a number of properties which limit its use as a sterilant. For example, EO is highly flammable and highly explosive. For this reason, all EO sterilization facilities must include damage-limiting construction and all equipment used in the EO sterilization process must be explosion proof. In addition, high concentrations of EO are acutely toxic for humans, and EO has been implicated as a carcinogen in laboratory animals. EO sterilization plants must, therefore, be outfitted with expensive equipment to minimize exposure of facility personnel to EO and to prevent escape of EO to the atmosphere outside the facility.
Another disadvantage of EO is that it reacts with chlorine to form ethylene chlorhydrin (ECH) and with water to form ethylene glycol (EG). Both of these byproducts are toxic and must be reduced to safe levels before sterilized materials are released for use. In fact, formation of ECH and EG preclude the use of EO for sterilization of a number of food products for which it would otherwise be a very useful sterilant.
Over the last fifty years, a number of other gases that lack one or more of the disadvantages of EO have been tested as sterilants. These gases include, for example, hydrogen peroxide, ozone and chlorine dioxide. However, no other gas has proven to be as efficacious as EO for use in large volume industrial sterilizers. The most common reason for failure of these gases as useful sterilants has been inadequate permeation of the gases through packaging materials and into lumens and interstices of the product being sterilized. Failure to permeate may be due to a number of factors including size of the sterilant molecule, reactivity of the sterilant molecule with outer packaging materials prior to reaching the target material, and degradation of the sterilant molecule prior to reaching the target material.
A number of commercial fumigants are presently used to treat foodstuffs and Other stored commodities. The most widely used fumigants are methyl bromide, hydrogen phosphide, carbon dioxide, and hydrogen cyanide. Many of these compounds pose hazardous conditions for application personnel and can form deleterious residues in the foodstuffs and commodities that are treated. Methyl bromide, the most widely used fumigant, has been identified as an ozone layer depleting agent and is slated, under the Montreal Protocols of 1997, to be banned by the year 2005. One important factor that differentiates the above listed fumigants from other sterilants is their ability to readily permeate granular or powdered products, which allows the fumigant to contact the infesting pests in such products.
Some of the above-mentioned traditional sterilants or fumigants have been identified with the formation of carcinogens and mutagens which thus limit the products that can be treated.
Other procedures that have been developed to treat products utilize heat, ionizing radiation, and other chemical compounds. All of these procedures are potentially detrimental to the products"" nutritional, physical and/or chemical attributes and thus make them undesirable.
Thus, a means to reduce biological loads in consumer products to eliminate human pathogens while maintaining product stability remains a necessity. Accordingly, there remains a need for better alternative methods and apparatus for reducing the biological load on consumer products.
It is desirable to treat a wide variety of consumer products in chamber type operations in a cost effective manner. The method and apparatus of the present invention permit sterilization or fumigation (hereinafter referred to as xe2x80x9cbiological burden reductionxe2x80x9d of a product in its original container (e.g., burlap bag, fiber drum, kraft paper bag, plastic bag, etc.). Thus, double handling, product loss, and post treatment contamination are reduced.
The method of the present invention utilizes a gaseous mixture containing O1, O2 and O3 (hereinafter referred to as xe2x80x9cOxxe2x80x9d) in a technologically advanced treatment system that overcomes the limitations formerly encountered with O3 treatment on biological burden. Prior O3 treatments include, for example, (1) the submersion of an article to be sterilized in ozone-containing water and the bubbling of ozonated water over the article (see, e.g., U.S. Pat. No. 4,517,159 to Karlson and U.S. Pat. No. 4,640,872 to Burleson); and (2) the static treatment of medical devices and food products with gaseous ozone (see, e.g., U.S. Pat. No. 3,179,017 to Shapiro et al., U.S. Pat. No. 5,069,880 to Karlson, and U.S. Pat. No. 5,120,512 to Masuda.) Systems utilizing ozone as a sterilant such as described above have encountered several limitations. The incorporation of ozone gas into water and hen submersion of items(s) to be sterilized or the spraying of ozone treated water onto the surface of item(s) to be sterilized limit the process to products that can be soaked in water. The few gaseous uses of ozone have been limited to the surface treatment of medical devices and the like due to the lack of adequate penetration into compacted products. Thus, although these past processes have proven the efficacy of ozone as a sterilant, the limitation of the use of ozone as a surface treatment has not presented ozone as a reliable sterilant or fumigant for products contained within commercial containers. Furthermore, until recently, high concentration ozone generators, which would have allowed the present invention to properly function, have not been commercially available. The present invention requites a relatively high concentration of Ox for an extended treatment period to assist the required permeation of the Ox into the substrate bring treated. In addition to the generation of the ozone molecule, the present invention also utilizes the quenching effect of other inert gases to assist ozone generation, thereby increasing the stability of the Ox radicals. A combination of oxygen, carbon dioxide, argon, and nitrogen have been used in the method of the present invention to achieve these factors. In addition to the benefits discussed above, the use of small quantities of con dioxide results in an increase in the rate of respiration in insects and some microbes, thus further aiding the action of the Ox gases. Furthermore, the presence of atmospheric nitrogen has been utilized in the food industry for many years to protect sensitive oils and fats from oxidative rancidity. Small quantities of nitrogen can be used in the method of the present invention to assist in the protection of sensitive food components as well as assisting in the stabilization of the Ox generation.
As an aid to understanding the invention, but without being limited thereby, the present invention is based on the discovery of the following:
1. That water submersion in O3 sterilization is unnecessary and, in many cases, undesirable;
2. That use of gaseous O3 in a static fashion, in many cases, does not provide adequate penetration of O3 into products being treated;
3. That treating a product in-situ (no repackaging needed) is desirable;
4. That the use of cooler temperatures, in many cases, is desirable; and
5. That the destruction of insects and thee eggs is desirable.
Accordingly, it is an object of the present invention to provide a method and apparatus for reducing biological burden from consumer products.
It is another object of the present invention to provide a method and apparatus for reducing biological burden from consumer products in a safe manner.
It is thus an object of the present invention to eliminate the health risks that are associated with the reduction of biological burden from consumer products.
It is a further object of the present invention to provide a simple, efficient and economical method and apparatus for reducing biological burden from consumer products that can be used at the site of production and/or packaging of such products.
In accordance with the above and other objects, the inventive method comprises applying a continuous stream of Ox gas to a material in a sealed biological burden reduction chamber. The continuous stream of Ox gas is prepared in an Ox generation cell, which contains a means for generating the Ox gas at a pressure less than about 20 lbs/in2 using, for example, one or more of the following: corona discharge, high frequency electrical discharge, ultraviolet light, x-ray, radioactive isotope and electron beam.
As discussed herein, a small percentage of N2, CO2 and/or Ar may be added during Ox treatment. The addition of 0% to 15% N2, 1% to 20% CO2 and/or 1% to 18% Ar increases the generation of an Ox quenching effect Penetration of Ox into the material being treated is thus enhanced. In addition, Argon is unique among the (inert) Noble Gases, in that it is soluble in both water and organic liquids. (The Merck Index Eleventh Edition). This characteristic theoretically enables Argon to become a glue of sorts. Argon is capable of attaching to gases without reacting thereto. Argon thus assists in Ox quenching by attaching to the Ox molecules and preventing the Ox molecules from colliding into each other. Argon also loosely binds hydrophilic and hydrophobic materials, thus allowing one to be diffused through the other, without reacting with either. This characteristic is useful in accelerating the diffusion of Ox into and through hydrophilic materials such as fats, oils and cell walls.
The inventive apparatus comprises:
(a) a biological burden reduction chamber;
(b) a vacuum pump coupled to the biological burden reduction chamber;
(c) an Ox generation cell, wherein the Ox generation cell contains a means for generating Ox at pressure less than about 20 lbs./in2 using, for example, one or more of the following: corona discharge, high frequency electrical discharge, ultraviolet light, x-ray, radioactive isotope and electron beam;
(d) a first control valve coupled to the biological burden reduction chamber and the Ox generation cell, wherein the first control valve is capable of permitting Ox to be drawn from the Ox generation cell into the biological burden reduction chamber; and
(e) a second control valve coupled to the biological burden reduction chamber, wherein the second control valve is capable of withdrawing Ox contained within the biological burden reduction chamber out of the biological burden reduction chamber.
Water vapor may be introduced to the gaseous Ox to maintain an appropriate humidity level, i.e., between about 20% and 98% relative humidity, and, more preferably between about 40% and 75% relative humidity. The appropriate humidity level is dependent upon the ambient humidity and upon the product being treated. For example, granular and powered products require a relatively low humidity level to prevent growth of mold and yeast thereon. However, depending on the length of treatment time, the vacuum created during the process removes humidity, thus requiring the addition of humidity. The Ox gas may then be passed through a commercially available catalytic destruct unit to eliminate any residual O3 and O1 before the gas stream is discharged to the atmosphere.
According to another aspect of the vacation, the Ox gas within the biological reduction chamber is agitated to increase permeation of the Ox into the material being treated. Any means of moving Ox within the chamber can be used. For example, forced air can be used to distribute the Ox evenly throughout the biological burden reduction chamber.
According to a further aspect of the invention, the Ox in the biological burden reduction chamber is maintained at a concentration of about 0.1% to about 100%, preferably 0.1% to 25%, and more preferably 3% to 16%, per total volume of gases in the biological burden reduction chamber. The amount of Ox employed depends upon the material being treated.
According to yet a further aspect of the invention, the water vapor present in the continuous stream of Ox can be controlled prior to applying the continuous stream of Ox to the material being treated.
Preferably, the pressure within the biological burden reduction chamber is maintained at a pressure between about 0 psia ad 20 psia.
The present invention is also directed to treated consumer products that result from use of the present inventive method and apparatus.
Additional objects and attendant advantages of the present invention will be set forth in the description and examples that follow, or may be learned from practicing the method or using the apparatus of the present invention. These and other objects and advantages may be realized and attained by means of the features, instrumentalities and/or combinations particularly described herein. It is also to be understood that the foregoing general description and the following detailed description are only exemplary and explanatory and are not to be viewed as limiting or restricting the invention as claimed.
The invention itself, together with further objects and attendant advantages, will best be understood by reference to the following detailed description, taken in conjunction with the accompanying drawings.